汶川8.0级地震序列及相关问题讨论
摘要
汶川8.0级地震序列具有明显的分段特性,较强余震分布于茂县、绵竹以南及平武以北。主破裂过程在中南段以逆冲为主,序列逐渐衰减,呈主余型的序列衰减特征;北段是汶川地震破裂过程的终止区域,主破裂过程在该区域以走滑为主,形成多震型的序列特征,也成为汶川序列较大余震的主体活动区域。序列较强余震活动明显受引潮力调制,大多数较强余震发生在固体潮大、小潮时段,并且16时前后是较强余震的优势发震时段。序列衰减系数p值随时间增加而逐渐增大,最终基本稳定在1附近变化。结合以往的研究,对序列类型及最大强余震震级、强余震活动持续时间等进行了初步讨论。初步的统计结果还显示,8级左右强震序列中主震与最大余震之间的震级差正比于主震破裂尺度,这意味着当震级大体接近时,较大的破裂尺度与较为充分的能量释放相对应。
Aftershock activity ofMay 12M8.0 W enchuan Earthquake sequence shows an obvious segmen-ted feature,most of the large aftershocks are d istributed in the south and north parts of aftershock zone.Thrusting is dom inant in the south partwith a small strike slip component.The aftershock activ-ity decays gradually and presents the sequence feature ofmainshock-aftershock pattern.The north part is the end ing area of the mainshock fracture,where the strike slipping is dom inant and shows an obvi-ous swarm feature,it therefore became the major area for large aftershocks.Modulation of earth tide on aftershock activity is remarkable,most of large aftershocks occur during the period of flood and neap tide.The time period around 16: 00 is the dom inant occurring time for large aftershocks.Thep-val-ue,a parameter ofmod ified Omori formula,increases gradually with time,and reaches about 1 in the final.Based on the previous study,the sequence patterns,magnitude ofmaximum aftershock,as well as the duration of aftershock activity have been d iscussed.The primary results also show that the mag-nitude d ifference between mainshock and the maximum aftershock is proportional to the rupture size of the mainshock for huge earthquakes of aboutM8.0.This means that,when the magnitudes of earth-quakes are nearly the same,large rupture size corresponds to the sufficient energy release.
Aftershock activity ofMay 12M8.0 W enchuan Earthquake sequence shows an obvious segmen-ted feature,most of the large aftershocks are d istributed in the south and north parts of aftershock zone.Thrusting is dom inant in the south partwith a small strike slip component.The aftershock activ-ity decays gradually and presents the sequence feature ofmainshock-aftershock pattern.The north part is the end ing area of the mainshock fracture,where the strike slipping is dom inant and shows an obvi-ous swarm feature,it therefore became the major area for large aftershocks.Modulation of earth tide on aftershock activity is remarkable,most of large aftershocks occur during the period of flood and neap tide.The time period around 16: 00 is the dom inant occurring time for large aftershocks.Thep-val-ue,a parameter ofmod ified Omori formula,increases gradually with time,and reaches about 1 in the final.Based on the previous study,the sequence patterns,magnitude ofmaximum aftershock,as well as the duration of aftershock activity have been d iscussed.The primary results also show that the mag-nitude d ifference between mainshock and the maximum aftershock is proportional to the rupture size of the mainshock for huge earthquakes of aboutM8.0.This means that,when the magnitudes of earth-quakes are nearly the same,large rupture size corresponds to the sufficient energy release.
引文
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刘蒲雄,陈修启,吕晓健,等.1996.地震序列的后续显著地震的预测研究[J].地震学报,18(1):27-33.LIU Pu-xiong,CHEN Xiu-qi,L Xiao-jian,et al.1996.Study on forecasting of large aftershocks in sequence[J].Acta Seismologica Sinica,9(1):31-39.
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吴开统,焦远碧,吕培苓,等.1990.地震序列概论[M].北京:北京大学出版社.97-98.WU Kai-tong,JIAO Yuan-bi,L Pei-ling,et al.1990.Conspectus of Earthquake Sequences[M].Peking UniversityPress,Beijing.97-98(in Chinese).
张培震,徐锡伟,闻学泽,等.2008.2008年汶川8·0级地震发震断裂的滑动速率、复发周期和构造成因[J].地球物理学报,51(4):1066-1073.ZHANG Pei-zhen,XU Xi-wei,WEN Xue-ze,et al.2008.Slip rates and recurrence intervals of the Longmen Shan ac-tive fault zone,and tectonic implications for the mechanism of the May12Wenchuan earthquake,2008,Sichuan,China[J].Chinese Journal of Geophysics,51(4):1066-1073(in Chinese).
赵志新,尾池和夫,松村一男,等.1992.中国大陆地震余震活动的p值[J].地震学报,14(1):9-16.ZHAO Zhi-xin,Matsumura K,Oike K,et al.1992.Thepvalue of aftershock activity in Chinese mainland[J].ActaSeismologica Sinica,14(1):9-16(in Chinese).
Das S and Henry C.2003.Spatial relation between main earthquake slip and its aftershock distribution[J].Reviewsof Geophysics,41,3/1013:1-23.
Heaton TH.1975.Tidal triggering of earthquakes[J].Geophys R Astr Soc,43(2):307-326.
Kisslinger C and Jones L M.1991.Properties of aftershocks in southern California[J].J Geophys Res,96:11947-11958.
Lomnitz C.1966a.Magnitude stability in earthquake sequences[J].Bull Seismol Soc Am,56:247-249.
Lomnitz C.1966b.Clustering in aftershock sequences[A].In:Steinhart J Set al(eds).The Earth Beneath the Con-tinents.AGU Geophysical Monograph10,AGU,Washington D C.502-508.
Papazachos B C.1974.On the time distribution of aftershocks and foreshocks in the area of Greece[J].PAGEOPH,112:627-631.
Tanakad S,Ohtake M,Sato H.2002.Eevdence for tidal triggering of earthquakes as revealed from statistical analysis ofglobal data[J].Geophys Res,107:2211-2221.
Utsu T,Ogata Y,Matsuura R S.1995.The centenary of the Omori formula for a decay lawof aftershock activity[J].J Phys Earth,43(1):1-33.
Utsu TA.1961.Statistical study on the occurrence of aftershocks[J].Geophys Mag,30:521-605.
Utsu T.1969.Aftershocks and earthquake statistics(Ⅰ):Some parameters which characterize aftershock sequence andtheir interrelation[J].J Fac Sci Hokkaido Univ,SerⅦ,(2):129-195.
Utsu T.1962.On the nature of three Alaskan aftershock sequences of1957and1958[J].Bull Seismol Soc Am,52:279-297.
陈运泰,许力生,张勇,等.2008.2008年5月12日汶川特大地震震源特性分析报告[R].http:∥www·csi·ac·cn/sichuan/chenyuntai.pdf.CHEN Yun-tai,XU li-sheng,ZHANG Yong,et al.2008.Report on the great Wenchuan earthquake source of May12,2008[R].http:∥www·csi·ac·cn/sichuan/chenyuntai.pdf(in Chinese).
谷继成,谢小碧,赵莉.1979.强余震的时空分布规律及其理论解释[J].地球物理学报,22(1):32-46.GU Ji-cheng,XIE Xiao-bi,ZHAO Li.1979.The spatial-temporal distribution rule of the large aftershocks and the theo-retical explanation[J].Chinese Journal of Geophysics,22(1):32-46(in Chinese).
蒋海昆,曲延军,李永莉,等.2006a.中国大陆中强地震余震序列的部分统计特征[J].地球物理学报,49(4):1110-1117.JIANG Hai-kun,QU Yan-jun,LI Yong-li,et al.2006a.Some statistic features of aftershock sequences in Chinese ma-inland[J].Chinese Journal of Geophysics,49(4):1110-1117(in Chinese).
蒋海昆,李永莉,曲延军,等.2006b.中国大陆中强地震序列类型空间分布特征[J].地震学报,28(4):389-398.JIANG Hai-kun,LI Yong-li,QUYan-jun,et al.2006b.Spatial distribution features of sequence types of moderate andlarge earthquake in Chinese mainland[J].Acta Seismologica Sinica,19(4):417-427.
蒋海昆,代磊,侯海峰,等.2006c.余震序列性质判定单参数判据的统计研究[J].地震,26(3):17-25.JIANG Hai-kun,DAI Lei,HOU Hai-feng,et al.2006c.Statistic study on the criterion index for classification of after-shock sequences[J].Earthquake,26(3):17-25(in Chinese).
蒋海昆,郑建常,吴琼,等.2007.中国大陆中强以上地震余震分布尺度的统计特征[J].地震学报,29(2):151-164.JIANG Hai-kun,ZHENG Jian-chang,WUQiong,et al.2007.Statistical features of aftershock distribution size for mod-erate or large earthquakes in Chinese mainland[J].Acta Seismologica Sinica,20(2):158-171.
刘蒲雄,陈修启,吕晓健,等.1996.地震序列的后续显著地震的预测研究[J].地震学报,18(1):27-33.LIU Pu-xiong,CHEN Xiu-qi,L Xiao-jian,et al.1996.Study on forecasting of large aftershocks in sequence[J].Acta Seismologica Sinica,9(1):31-39.
王林瑛,舒曦.1997.利用熵值及多分形方法研究地震序列类型的早期判定[A].见:国家地震局预测预防司编.地震短临预报的理论与方法:"八五"攻关三级课题论文集.北京:地震出版社.136-142.WANG Lin-ying,SHU Xi.1997.Early determination of earthquake sequence types using entropic thresholding andmultifractal model[A].In:Department of Earthquake Hazard Prevention,SSB(ed).Collected Papers on Theo-ries and Methods of Short-term and Imminent Earthquake Prediction:Three-level Key-problem-tackling Projects ofthe National8th"5-Year Plan".Seismological Press,Beijing.136-142(in Chinese).
吴开统,焦远碧,吕培苓,等.1990.地震序列概论[M].北京:北京大学出版社.97-98.WU Kai-tong,JIAO Yuan-bi,L Pei-ling,et al.1990.Conspectus of Earthquake Sequences[M].Peking UniversityPress,Beijing.97-98(in Chinese).
张培震,徐锡伟,闻学泽,等.2008.2008年汶川8·0级地震发震断裂的滑动速率、复发周期和构造成因[J].地球物理学报,51(4):1066-1073.ZHANG Pei-zhen,XU Xi-wei,WEN Xue-ze,et al.2008.Slip rates and recurrence intervals of the Longmen Shan ac-tive fault zone,and tectonic implications for the mechanism of the May12Wenchuan earthquake,2008,Sichuan,China[J].Chinese Journal of Geophysics,51(4):1066-1073(in Chinese).
赵志新,尾池和夫,松村一男,等.1992.中国大陆地震余震活动的p值[J].地震学报,14(1):9-16.ZHAO Zhi-xin,Matsumura K,Oike K,et al.1992.Thepvalue of aftershock activity in Chinese mainland[J].ActaSeismologica Sinica,14(1):9-16(in Chinese).
Das S and Henry C.2003.Spatial relation between main earthquake slip and its aftershock distribution[J].Reviewsof Geophysics,41,3/1013:1-23.
Heaton TH.1975.Tidal triggering of earthquakes[J].Geophys R Astr Soc,43(2):307-326.
Kisslinger C and Jones L M.1991.Properties of aftershocks in southern California[J].J Geophys Res,96:11947-11958.
Lomnitz C.1966a.Magnitude stability in earthquake sequences[J].Bull Seismol Soc Am,56:247-249.
Lomnitz C.1966b.Clustering in aftershock sequences[A].In:Steinhart J Set al(eds).The Earth Beneath the Con-tinents.AGU Geophysical Monograph10,AGU,Washington D C.502-508.
Papazachos B C.1974.On the time distribution of aftershocks and foreshocks in the area of Greece[J].PAGEOPH,112:627-631.
Tanakad S,Ohtake M,Sato H.2002.Eevdence for tidal triggering of earthquakes as revealed from statistical analysis ofglobal data[J].Geophys Res,107:2211-2221.
Utsu T,Ogata Y,Matsuura R S.1995.The centenary of the Omori formula for a decay lawof aftershock activity[J].J Phys Earth,43(1):1-33.
Utsu TA.1961.Statistical study on the occurrence of aftershocks[J].Geophys Mag,30:521-605.
Utsu T.1969.Aftershocks and earthquake statistics(Ⅰ):Some parameters which characterize aftershock sequence andtheir interrelation[J].J Fac Sci Hokkaido Univ,SerⅦ,(2):129-195.
Utsu T.1962.On the nature of three Alaskan aftershock sequences of1957and1958[J].Bull Seismol Soc Am,52:279-297.
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